(1) Field of the Invention
The present invention relates to a method for improving stool characteristics in infants.
(2) Description of the Related Art
The infant gut microflora is rapidly established in the first few weeks following birth. The nature of this intestinal colonization is initially determined by early exposure to environmental sources of microbes as well as the health of the infant. Whether the infant is breast-fed or formula fed also has a strong influence on the intestinal bacterial population.
In the breast-fed infant, for example, Bifidobacterium spp. dominate among intestinal bacteria, with Streptococcus spp. and Lactobacillus spp. as less common contributors. In contrast, the microflora of formula-fed infants is more diverse, containing Bifidobacterium spp. and Bacteroides spp. as well as the more pathogenic species, Staphylococcus, Escherichia coli and Clostridia. The varied species of Bifidobacterium in the stools of breast-fed and formula-fed infants differ as well.
Bifidobacteria are generally considered “beneficial” bacteria and are known to protect against colonization by pathogenic bacteria. This likely occurs through competition for cell surface receptors, competition for essential nutrients, production of anti-microbial agents, and production of inhibitory compounds such as short chain fatty acids (SCFA) which may decrease fecal pH and inhibit potentially pathogenic bacteria. Bifidobacteria are also associated with resistance to gastrointestinal (GI) tract and respiratory infection as well as an enhanced immune function in children and infants. Therefore, the promotion of an intestinal environment in which Bifidobacteria dominate has become a goal in the development of nutritional formulations for formula-fed infants.
Human milk (HM) contains a number of factors that may contribute to the growth and population of Bifidobacteria in the gut microflora of infants. Among these factors is a complex mixture of more than 130 different oligosaccharides that reach levels as high as 8-12 g/L in transitional and mature milk. Kunz, et al., Oligosaccharides in Human Milk: Structure, Functional and Metabolic Aspects, Ann. Rev. Nutr. 20: 699-722 (2000). These oligosaccharides are resistant to enzymatic digestion in the upper gastrointestinal tract and reach the colon intact, where they serve as substrates for colonic fermentation.
HM oligosaccharides are believed to elicit an increase in the number of Bifidobacteria in the colonic flora, along with a reduction in the number of potentially pathogenic bacteria. Kunz, et al., Oligosaccharides in Human Milk: Structure, Functional and Metabolic Aspects, Ann. Rev. Nutr. 20: 699-722 (2000); Newburg, Do the Binding Properties of Oligosaccharides in Milk Protect Human Infants from Gastrointestinal Bacteria?, J. Nutr. 217:S980-S984 (1997). One way that HM oligosaccharides may increase the number of Bifidobacteria and reduce the number of potentially pathogenic bacteria is by acting as competitive receptors and inhibiting the binding of pathogens to the cell surface. Rivero-Urgell, et al., Oligosaccharides: Application in Infant Food, Early Hum. Dev. 65(S):43-52 (2001).
Because cow's milk and commercially available infant formulas that are based on cow's milk provide only trace amounts of oligosaccharides, however, prebiotics are often used to supplement the diet of formula-fed infants. Prebiotics have been defined as “non-digestible food ingredients that beneficially affect the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon that can improve the health of the host”. Gibson, G. R. & Roberfroid, M. B., Dietary Modulation of the Human Colonic Microbiota-Introducing the Concept of Probiotics, J. Nutr. 125:1401-1412 (1995). Common prebiotics include fructo-oligosaccharide, gluco-oligosaccharide, galacto-oligosaccharide, isomalto-oligosaccharide, xylo-oligosaccharide and lactulose.
Unfortunately, however, there are some disadvantages in the administration of prebiotics to formula-fed infants. While they may beneficially affect the population of beneficial bacteria in the gut, the fermentation of many of these prebiotic substances occurs at a very rapid rate, which often produces excess gas, abdominal distension, bloating, and diarrhea. Human milk contains very high levels of oligosaccharides, in fact, approximately 10% of the total carbohydrates are oligosaccharides. Adding such significant concentrations of prebiotics to infant formulas causes unusually loose stools and diarrhea. Diarrhea and loose stools can severely compromise infant health due to depletion of fluids, electrolytes, and other nutrients. Accordingly, it would be beneficial to provide prebiotics to an infant in a method that would benefit the gut microflora without producing unwanted side effects such as those discussed above.